Custom Permalink with child categories creating 404
I am trying to have a permalink strucutre as follows:
/category [List all the posts for the category] /category/child-category [List all the posts for the child category] /category/post-slug
My permalink settings is as follows:
The category base is blank.
But if I navigate to /category/child-category from the URL bar, the link 404s. It only works when I navigate to /child-category without the parent category from the URL bar.
What would I need to do to have the permalink structure that I am trying to accomplish?